Non Patent Literature 1 discloses epitaxial growth of GaN on a (100) β-Ga2O3 substrate by the metal-organic vapor phase epitaxy process. In the epitaxial growth of GaN, a low-temperature GaN buffer layer is grown at 600 Celsius degrees on the Ga2O3 substrate. A GaN layer of 1000 nm is grown at 1070 Celsius degrees directly on this low-temperature GaN buffer layer.
Non Patent Literature 2 discloses an InGaN light emitting diode. The light emitting diode uses a patterned sapphire substrate and plural gallium nitride based semiconductor layers are grown through a buffer layer on this sapphire substrate. The pattern formation of the sapphire substrate can improve extraction efficiency of light.
Non Patent Literature 3 discloses an InGaN—GaN light emitting diode. This light emitting diode includes a GaN-based film grown on a sapphire substrate. The sapphire substrate is separated from the GaN-based film, using a laser beam.